The present invention applies to pellet molding apparatus and particularly to the type of pellet molding apparatus capable of molding log fire starting pellets composed of a material which must be molded under controlled time and pressure and in a particular manner to permit ejection of the pellet from the mold members.
There is currently in existence a number of different types of pellet or capsule molding machines which are used to form pellets from different materials such as chlorine for swimming pools, the commonly known aspirin tablet and other types of tablets. In one form of these type of machines, a die is used into which there is placed a measured quantity of material to be compressed and the compression occurs by means of a fixed displacement ram operated by a cam or other positive displacement mechanism. In these machines, the pressure applied to the material being compressed will vary if the quantity of material placed into the ram is slightly above or below the exact amount required. Machines of this nature can operate under high speed and are suitable for pelletizing material of a nature in which the pressure applied is not critical.
Another form of machine used to create large pellets such as the chlorine pellets or tablets operates upon the principle of impacting the material placed within a ram and punch. This machine operates much on the common known principle of the punch press and impacts the material by means of the kinetic energy of a flywheel or other impact member. Again, these machines operate at a relatively high speed but the material upon which they are operating must be of the type that can be compressed quickly and which is not sensitive to fluctuation in pressures.
A third general category of tablet or pellet forming machine utilizes pneumatics as the pressure applying medium operating against a ram in conjunction with a die into which a metered amount of the material to be compressed has been placed. Again, these machines operate on a relatively high speed. However, the characteristic of pneumatic pressure, while capable of generating large pressures often necessary in forming some pellets, is not capable of applying a uniform pressure over a predetermined distance with a controlled rate of descent of the ram member.
The foregoing described machines for making pellets or tablets will not work effectively on all types of material which may be desired to be formed into pellets. One example of such a material is that used to form igneous slow burning pellets used to start wood fires in fireplaces. This material is formed of a composition of, primarily, sawdust and paraffin together with other organic materials. One example of the ingredients of such a material is that set forth in U.S. Pat. No. 3,988,121.
Forming pellets from the sawdust-paraffin composition material presents several problems. One great problem is that the composition of the paraffin in conjunction with the sawdust, in order to be formed into a stable pellet, must be subjected to a uniform controlled pressure over a finite period of time sufficient to permit the paraffin to flow and reform in the configuration of the pellet. Too rapid or uneven application of pressure to the sawdust-paraffin composition results in fractured pellets and/or uneven density and disintegrating pellets.
Another problem encountered with the sawdust-paraffin composition in the process of pelletizing the material is that the composition, after compression, exhibits significant adhesion to the walls of the die requiring undue pressure to remove the material upwardly from the die in the direction opposite to which it was compressed. The forces required for removal often results in fracture and destruction of the pellet.